As an organopolysiloxane which has a carboxyl group and is used as a surface treatment agent, a carboxyl group-containing organopolysiloxane is known from JP 9-59125A. Powder treated with the organopolysiloxane, however, does not have satisfactory water-resistance.
The following organopolysiloxane having two carboxyl groups is known from JP 2002-114849A.
wherein X is —O— or —NH—, M is a hydrogen atom, metal, ammonium or the like. Powder treated with the organopolysiloxane, however, does not have satisfactory water-resistance, which is presumably due to the presence of many polar groups, i.e., amide and carbonyl groups, in the organopolysiloxane.
The organopolysiloxane described in WO 03/095530 A1 and WO 03/094871 A1 does not have amide or carbonyl groups.

However, powder surface-treated with the organopolysiloxane does not satisfactorily disperse in an unctuous agent such as isododecane.